Solid rivets are used extensively to fasten parts in a variety of applications. In the aircraft industry, rivets are commonly used to join structural members and to fasten exterior skins on airframes. In the case of relatively soft rivets, one end of the rivet may be upset using high impulse forces from a rivet gun. However, where the rivet is relatively hard, the upset process is performed by squeezing the rivet between an anvil and a forming die. One type of apparatus used to squeeze rivets includes a C-shape frame having a pair of opposing jaws defining a throat into which a workpiece may be placed. One of the jaws includes a tool in the form of an anvil that bears against one end of the rivet, sometimes referred to as the “factory head”. A linear actuator mounted on the other jaw includes a forming die that engages the opposite end of the rivet, sometimes referred to as the bucktail. With the factory head held against the anvil, the actuator pushes the forming die into the bucktail, deforming the end of the rivet to create a button, thereby upsetting the rivet in place.
The linear actuator described above may be hydraulic, pneumatic or electromagnetic, and usually includes an elongate cylinder or body that extends outwardly from the C-shape frame. In some applications, the geometry and placement of the actuator on the C-shape frame may result in physical interference between the actuator cylinder and the workpiece that prevents the jaws from being positioned around the rivets. For example, a workpiece to be riveted may be held and clamped in place on jigs and/or fixtures on an interior side of the workpiece where the bucktails of the rivets are located. These structural interferences and the size of the actuator may prevent the button forming jaw from being positioned in back of the rivet.
One solution to the problem discussed above involves moving the actuator to the opposite jaw so that the anvil is driven into the factory head of the rivet. This solution is not satisfactory in many applications where pushing on the manufactured head of the rivet may result in damage to the rivet and/or the parts being fastened.
Accordingly, there is a need for a method and apparatus for squeezing rivets that overcome the problems discussed above. Embodiments of the present disclosure are intended to provide a solution to these problems.